Device for deep-rolling transition radii on crankshafts

ABSTRACT

Disclosed is a device for deep-rolling transition radii ( 5, 6 ) of crankshafts ( 1 ). Said device comprises at least one ruler-shaped rolling element ( 12, 13 ) that can be moved back and forth in one direction and has a substantially rectilinear contact surface ( 14, 15 ), a corresponding guiding surface for introducing a deep-rolling force (F) into a transition radius ( 5, 6 ) of a crankshaft ( 1 ), said guiding surface lying across from the guiding surface ( 14, 15 ) at a certain distance, and a means which generates a guiding and pressing force of the rolling element ( 12, 13 ). Said means consists of a guiding roller ( 29 ) which is rotatably mounted in the housing ( 18 ) of a deep-rolling tool ( 11 ) and has a circular guiding surface ( 24, 25 ) in relation to the guiding roller ( 29 ). The guiding surface of the rolling element ( 12, 13 ) adapts to said circular guiding surface ( 24, 25 ).

The invention relates to a device for deep-rolling transition radii on crankshafts, having at least one straight-edged roller element which may be moved back and forth in a direction and which has an essentially linear contact surface, a corresponding guide surface spaced at a distance opposite from the guide surface for introducing a deep-rolling force into a transition radius of a crankshaft, and a means which produces guiding and a pressure force for the roller element.

A method and a device for strengthening crankshafts is known from EP 1 779 972 A2. The device describes two straight-edged, essentially linear roller elements of finite length which penetrate with a contact surface into the transition radius of a bearing journal of a crankshaft, under a deep-rolling force. The crankshaft is supported with respect to the penetrating roller elements by a support element which is known per se. The support element is composed, for example, of a prismatic straight-edge or of support rollers situated in a support roller head. A force introduction region is situated at a distance from the contact surfaces. In the known case, the force introduction region is a flat surface on which the deep-rolling force, which is introduced into the crankshaft in the contact surface region, acts. In the cited document little is stated about the introduction of the rolling forces, only the following: “The rolling forces are introduced into the roller element according to the invention via suitable means in a force introduction region which is preferably provided essentially in the region of the roller element situated opposite from the contact surface, relative to the longitudinal axis of the roller element” (see EP 1 779 972 A2, column 12, lines 28-39). Another passage in the document reads as follows: “For this purpose, a device according to the invention for deep-rolling the transition radii of crankshafts has suitable means or devices which produce corresponding guiding or a pressure force for the roller element” (see EP 1 779 972, A2 column 13, lines 24-29). In the known document, the information concerning the possibilities for applying the deep-rolling force to the roller elements is limited to the general statement of means which are suitable for carrying out such tasks. In fact, however, such information is not sufficient for indicating to one skilled in the art an approach which he can use, absent of inventive activity, in order to apply the deep-rolling force to the straight-edged roller elements.

The object of the present invention, therefore, is to provide suitable means which allow introduction of the deep-rolling force into the straight-edged roller elements.

According to the invention, for this purpose a means is proposed which is composed of a guide roller which is rotatably mounted in the housing of a deep-rolling tool, and with reference to the guide roller has a circular guide surface to which the guide surface of the rolling element conforms. For this purpose it is thus proposed herein to provide a guide roller of a deep-rolling tool, which is known per se in conjunction with deep-rolling rollers, to transmit the deep-rolling force to the straight-edged roller elements and to simultaneously guide the roller elements in their working direction.

According to one advantageous embodiment, the guide surfaces of the guide roller and the roller element are curved. This curvature, which refers to the cross section of the guide roller as well as of the roller elements, preferably has the shape of a circular arc.

According to a further advantageous exemplary embodiment, the contact surface of the roller element has a radius of curvature with respect to the crankshaft which is smaller than the radius of curvature of the guide surface of the roller element. This results in different surface pressures in the region of the guide surfaces of the roller element and the guide roller, and in the region of the contact surface and the transition of the crankshaft. The contact surface of the roller element may also be curved in its longitudinal extension, as provided in EP 1 779 972 A2 (see column 13, lines 35-39).

It is also advantageous when the guide roller is mounted in the housing so as to be laterally movable in the direction of its rotational axis. In this manner irregularities in the transition radii of a crankshaft, which inevitably always occur, may be compensated for by displacing the guide roller within the deep-rolling tool. As a result, for an axial motion of the guide roller the roller elements swivel about a longitudinal axis located in the direction of the longitudinal extension of the roller elements.

As a rule, two parallel roller elements are provided within a deep-rolling tool, one roller element for each transition radius. The two roller elements are held on the housing of the deep-rolling tool by a captive retainer. In cooperation with the captive retainer, a connecting spring may be provided, for example, at each of the two ends of the oblong roller elements.

The invention is described in greater detail below with reference to one exemplary embodiment.

The figures show the following, in each case in a simplified manner and not to scale:

FIG. 1 shows a crank pin of a crankshaft together with a deep-rolling tool, in a side view;

FIG. 2 shows a cross section of the deep-rolling tool along line II-II of FIG. 1;

FIG. 3 shows a cross section of the deep-rolling tool along one of lines or III′-III′ of FIG. 1; and

FIG. 4 shows a section of the deep-rolling tool, viewed in one of directions A or B.

A bearing journal 2 of a crankshaft 1 is schematically illustrated in FIG. 1. The bearing journal 2 may be a main bearing journal or a stroke bearing journal. The respective rotational axis of the bearing journal 2 is indicated by the dash-dotted line 3. The cylindrical surface 4 of the bearing journal 2 is delimited on both sides by transition radii 5 and 6, which in the present case are designed as turned grooves. The transition radii 5 and 6 are adjoined by oil collars 7 and 8, which merge into the cheeks 9 and 10 of the crankshaft 1.

The deep-rolling tool 11 is composed of two straight-edged roller elements 12 and 13, shown in cross section in FIG. 2. The two roller elements 12 and 13 penetrate with their respective contact surfaces 14 and 15 into the transition radii 5 and 6 under the action of a deep-rolling force F. The deep-rolling force F is applied to the roller elements 12 and 13 by means of a guide roller 29, which at the same time performs the guiding of the two roller elements 12 and 13 in their longitudinal direction, i.e., perpendicular to the plane of the drawing in FIG. 2. In the present example of FIG. 2, the guide roller 29 as well as roller elements 12 and 13 are illustrated in cross section. The guide roller 29 is rotatably mounted in the housing 18 of the deep-rolling tool 11 by means of a bolt 16 and a needle bearing 17. The deep-rolling force F is applied to the two roller elements 12 and 13 via the housing 18 and the guide roller 29. At the same time, the guide roller 29 rotatably mounted in the housing 18 has limited mobility in the axial direction 19. As a result of the axial mobility 19 of the guide roller 29, the roller elements 12 and 13 are able to swivel about their respective longitudinal axes 20 and 21. Irregularities in the transition radii 5 and 6 may be compensated for due to this movable adjustability.

The two roller elements 12 and 13 are each rounded with a first corner radius 22 in contact surfaces 14 and 15. In each case a corner radius 23 of the guide surface 35, with which the two roller elements 12 and 13 are rounded on their opposite side, is situated opposite from this corner radius 22. It is apparent that the second corner radius 23 is much larger than the first corner radius 22. Over the guide surface 35 the two roller elements 12 and 13 each conform to the two circular guide surfaces 24 and 25, respectively, of the guide roller 29. The term “circular” regarding the guide surfaces 24 and 25 is understood with respect to the roller-shaped design of the guide roller 29. In fact, in their cross section the guide surfaces 24 and 25 may have a corner radius which has other possible contours besides the circular shape, for example an ellipsoidal shape or the like.

Since the two roller elements 12 and 13 project beyond the housing 18 of the deep-rolling tool 11 with their longitudinal extension, a captive retainer 26 is also provided on the housing 18. As shown in FIG. 1, the captive retainer 26 is mounted on the two end-face ends 27 of the housing 18.

There are various options for designing a captive retainer 26. It is important that the captive retainer 26 fixes the roller elements 12 and 13 in a position on the housing 18 of the deep-rolling tool 11 which on the one hand allows the roller elements 12 and 13 a certain rotational mobility about their respective longitudinal axes 20 and 21, and on the other hand prevents the roller elements 12 and 13 from falling out of the deep-rolling tool 11. One example of a possibility for fixing the two roller elements 12 and 13 is to use metal sheets 28, for example, which are mounted on the end-face ends 27 of the housing 18.

According to one preferred embodiment, the roller elements 12 and 13 may have cross-sectional shapes which differ from one another. These differing cross-sectional shapes are mentioned here by way of example only. Thus, the accommodation of roller elements 12 and 13 having differing cross-sectional shapes in the very same deep-rolling device 11 is not provided. Rather, such a deep-rolling device has either two roller elements 12 of the same first cross-sectional shape, or two roller elements 13 which have differing second cross-sectional shapes. The preferred cross-sectional shape in each case depends on the particular operating conditions of the deep-rolling tool 11 and the available space.

In addition to the guide roller 29, two guide support rollers 30 and 31 are provided in the housing 18 of the deep-rolling tool 11. The guide support rollers 30 and 31 ensure that the linear roller elements 12, 13 each maintain their orthogonal position relative to the rotational axis 3 of the crank pin 2 and also with respect to the deep-rolling tool 11, regardless of the extent of the projection 32 or 33 of the roller elements 12 and 13 as a function of the particular rotational position 34 of the crank pin 2.

LIST OF REFERENCE NUMERALS

1 Crankshaft

2 Bearing journal

3 Rotational axis

4 Cylindrical surface

5 Transition radius

6 Transition radius

7 Oil collar

8 Oil collar

9 Cheek

10 Cheek

11 Deep-rolling tool

12 Roller element

13 Roller element

14 Contact surface

15 Contact surface

16 Bolt

17 Needle bearing

18 Housing

19 Axial direction

20 Longitudinal axis

21 Longitudinal axis

22 Corner radius

23 Corner radius

24 Circular guide surface

25 Circular guide surface

26 Captive retainer

27 End-face end

28 Metal sheet

29 Guide roller

30 Guide support roller

31 Guide support roller

32 Projection

33 Projection

34 Rotational position

35 Guide surface

F Deep-rolling force 

1. Device for deep-rolling transition radii on crankshafts, having at least one straight-edged roller element which may be moved back and forth in a direction and which has an essentially linear contact surface, a corresponding guide surface spaced at a distance opposite from the guide surface for introducing a deep-rolling force into a transition radius of a crankshaft, and a means which produces guiding and a pressure force for the roller element, characterized in that the means is composed of a guide roller which is rotatably mounted in the housing of a deep-rolling tool and, with reference to the guide roller, has a circular guide surface to which the guide surface of the rolling element conforms.
 2. Device according to claim 1, characterized in that the cross sections of the guide surfaces of the guide roller and of the roller element are curved.
 3. Device according to claim 1, characterized in that the contact surface of the roller element has a first corner radius which is smaller than the second corner radius of the guide surface.
 4. Device according to claim 1, characterized in that the contact surface of the roller element is curved in its longitudinal extension.
 5. Device according to claim 1, characterized in that the guide roller is mounted in the housing so as to be movable in the axial direction.
 6. Device according to claim 1, characterized in that two parallel roller elements are provided which are held by at least one captive retainer.
 7. Device according to claim 1, characterized in that the roller elements are mounted so as to be pivotable about a longitudinal axis.
 8. Device according to claim 1, characterized in that guide support rollers are provided as additional support of the roller elements in their respective longitudinal extension. 